Royal fans were delighted with the Father's Day tribute, with one user writing: "I love this. No self promotion, simple words that encompass and apply to all. Two lovely pictures that show us what it means to William! Happy Father's Day!".
But others questioned why the Cambridges chose to leave their other children, Prince George and Princess Charlotte, out of the post.
One user also noted there was no picture of the Duchess with her father, Michael Middleton, while another said it was unusual there had been no royal post for Mother's Day.
A fan account wondered whether the rumoured royal rift between Cambridges and the Sussexes, Prince Harry and Meghan Markle, was the reason behind the missed Mother's Day tribute, writing: "It’s strange that there was no post for Mother’s Day 🤔 maybe there’ll be one next year. Perhaps they were too busy with the brothers splitting their Instagram accounts 💕"
This year is the first time Prince Harry celebrates Father's Day following the birth of his first child Archie Harrison Mountbatten-Windsor.
The Duke and Duchess of Sussex marked the day with a stunning new picture of baby Archie holding his dad's finger on their Instagram account, with the caption: "Happy Father’s Day! And wishing a very special first Father’s Day to The Duke of Sussex!"
The Prince of Wales also shared a lovely shot with Prince William and Prince Harry on his and Camilla, Duchess of Cornwall's official social media account Clarence House, with the simple caption: "To Dads everywhere, have a wonderful #FathersDay."